"gradual, planned removal or elimination," 1958, from the verbal phrase (1954; see phase (v.)).
also freakout "bad psychedelic drug trip," or something comparable to one, 1966, from verbal phrase freak out, attested from 1965 in the drug sense (from 1902 in a sense "change, distort, come out of alignment"); see freak (n.). There is a coincidental appearance of the phrase in "Fanny Hill:"
She had had her freak out, and had pretty plentifully drowned her curiosity in a glut of pleasure .... [Cleland, "Memoirs of a Woman of Pleasure," 1749]
where the sense is "she had concluded her prank."
"offended, angry, upset," by 1887, from the verbal phrase in the sense of "offend," attested by 1822; see put (v.) + out (adv.). Perhaps via the earlier sense of "cause to lose self-possession, disconcert" (1580s). The verbal phrase is from mid-14c. as "drive out, banish, exile;" from 1520s as "extinguish" (a fire or burning object). To put out, of a woman, "to offer oneself for sex" is attested by 1947.